Hello,

Please add this code to the Theme Settings > Custom CSS > Global:

body .whb-sticked .main-nav .item-level-0.current-menu-item > a   {
    color:red;
	background:yellow;
}
body .whb-sticked .main-nav .item-level-0 > a {
    color: yellow;
}
body .whb-sticked .main-nav .item-level-0 > a:hover {
    color: orange;
	background:yellow;
}

Best Regards